In a magnetic recording/reproducing apparatus for recording and reproducing data signals with high density on and from a magnetic tape, a helical-scan recording method is employed using a rotary magnetic head (hereinafter referred to as “head”). The data signals are divided and recorded on a group of sequential unconnected slant tracks that are oblique to a longitudinal direction of the magnetic tape. A tracking control is performed to keep the head to follow the tracks during reproduction of the recorded data signals.
Conventional tracking control techniques using a control data obtained from a rotary head include, for instance, an ATF control method disclosed in the Television Technology, September 1985 edition, page 25–27, and a timing control method disclosed in Japanese Patent Laid-Open Publication No. 07-29256, page 3. In the ATF control method, a pilot signal is recorded either in a burst-like manner on a part of a track, or superposed on a data signal, and this pilot signal is used to perform the tracking control at the time of reproduction.
In the timing control method, the tracking control is performed using a tracking error data detected from a time difference between a rotation phase signal of a rotary drum (hereinafter referred to as “PG signal”) and a timing signal (hereinafter referred to in this invention as “synchronizing signal”) recorded on a track.
With the above-cited ATF control method, the data becomes redundantly long because it needs to record the pilot signal beside a data signal, and it makes worse the tracking accuracy due to residual pilot signal not completely erased on the track base when another data signal is overwritten.
In the timing control method, a difference in timing from a PG signal to a synchronizing signal recorded on a track is likely to receive an influence of irregular rotation of the rotary drum, vibration of the magnetic tape (hereinafter referred to as “jitter” of the rotary drum) and so forth, that also make worse the tracking accuracy.
With an advancement of high-density digital recording in recent years, it has become important to enhance accuracy of tracking control technique with narrow tracks.
In the timing control method, as discussed above, since there are large distances from a position of detecting the PG signal to positions of detecting the individual synchronizing signals, a timing error is liable to get influence of jitter and off-centered shaft of a rotary drum. It is especially difficult to obtain accurate tracking error data, as the closer the synchronizing signal is to a tail end of the track the greater the influence of jitter and off-centered shaft of the rotary drum. Furthermore, the influence of jitter and off-centered shaft of the rotary drum becomes even more significant if the rotary drum is small and light in weight.